When ProPublica and National Public Radio partnered for the series “Lost Mothers,” they discovered an alarming trend: The United States had the highest rate of women who die during pregnancy, childbirth and postpartum in the developed world despite spending more on healthcare than any other country. As reporters dug deeper into the data, a vital element was missing. Where were the mothers? “When a pregnant woman or a new mother dies in the U.S., we discovered she is almost invisible. He...